Kathy Schilla couldn't understand why her daughter, a third-grader, didn't want to go to school anymore. After much coaxing, the child finally revealed what had happened to her at Lester Park Elementary School in Duluth, Minn.

Her teacher, Douglas J. Ranthum, had asked her to model her talent-show costume in the cloakroom during recess. He told her to remove her underwear because it showed through her costume, and then he repeatedly touched her breasts and buttocks.

Her horrified parents went immediately to the principal, who mentioned that two other parents had complained about the same thing several months earlier.

The principal's suggestion was that the Schillas should have a talk with the teacher.

That was in 1984. Eventually, Ranthum was sent to prison, and the principal was reprimanded for failing to report sexual abuse.

But Ranthum's teaching certificate was suspended, not revoked. After his prison term, he went on to get four more teaching jobs, simply leaving each one when his past caught up with him.

He landed his last teaching job in 1995 at AlBrook Elementary School near Duluth, just months before the state began requiring criminal background checks. He remained there until Kathy Schilla tracked him down and notified school authorities of his conviction.

By then, Ranthum was a tenured teacher. No evidence was found that Ranthum was still molesting children. Still, the school district paid him $35,000 to leave in 1997.

In June of this year, 15 years after he molested Schilla's daughter, Ranthum's Minnesota teaching license was finally revoked.

Fingerprinting could have stopped Ranthum from circulating. Checking and cataloging fingerprints of teacher applicants is considered a fairly simple and nearly foolproof way to keep bad teachers -- at least, those who have been charged or convicted -- out of the classroom.

"I am shocked at the number of states that don't require fingerprinting," said Thomas W. Pickrell, director of legal services for the Arizona School Boards Association. Currently, 27 states require fingerprinting for all teaching license applicants. In Pennsylvania, only applicants who have been state residents for less than a year must be fingerprinted before getting a teaching certificate, while Ohio requires fingerprinting for all teachers. In West Virginia, no fingerprinting is required for certification, but all county school districts require fingerprinting before a teacher is hired.

Fingerprinting has been required since 1994 in Arizona, and last year, a statewide fingerprint database was created.

In Colorado, where fingerprinting also is required, a "tickler file" was established this year. If anyone holding a teaching certificate is arrested for any crime, his or her name is reported by law enforcement officials to the education department.

In New York, some state senators for years have been trying without success to pass a fingerprinting law. This year, the bill again passed in the state Senate but, again, was not approved by the state Assembly. Teacher unions have been opposed to mandatory fingerprinting, saying it's an invasion of privacy.

According to New York state senate spokesman Mark Hansen, the proposed bill not only would have required fingerprinting, it would have established a standard procedure for schools to investigate allegations of abuse. Hansen expects the bill to be reintroduced in January.

However, a state task force on school violence recently agreed to add to its recommendations a mandate for fingerprinting and a requirement that school officials report any suspicions of abuse to state officials within 48 hours. Punishment for failure to do so would include fines or license review.

Bart Zabin, an investigator with the New York State Department of Education, is angered by the lack of support for the fingerprinting bill. He's also concerned that bad teachers will be more likely to apply for a job in his state.

"I'd be sure to pick a state that didn't have fingerprinting if I were a criminal," he said.

But no matter how advanced the technology or how progressive the legislation, there's always a way to beat the system. Sex offenders are especially creative in finding ways to cover their tracks and continue molesting.

Take Julio Wilson, for example. When he filled out his criminal record application, required of anyone who wants to become a teacher in Pennsylvania, Julio Wilson became Julia Wilson.

With a false name and fake social security number he got from the Internet, his background check came out clean. However, soon after he started working as a special education teacher in Carlisle Area School District, the dirt began to surface.

It started with an angry mother's call to the state Department of Education. Julio Wilson, she said, had molested her daughter when he was a teacher in a non-public school in Pennsylvania. He had pled guilty to aggravated assault, corruption of minors and giving alcohol to minors, among other charges.

How, she wanted to know, could he be allowed to work in Carlisle?

In Wilson's case, state officials said they might never have learned about Wilson's background had it not been for that call. They began revocation proceedings and took his teaching license in 1996.

Most states run background checks on teacher applicants, but they're not infallible, said Pittsburgh police Acting Commander Lt. Tom Atkins. Besides the problem of false social security numbers, he said, "human error can come into play -- if a name is typed incorrectly, for instance. If you are looking for someone named Duane, and you type in Dane, it won't come up."

"We can't rely on technology," said Michele Haskins, a Pennsylvania education department spokeswoman. "We have to rely on people."

Sixteen states, including Mississippi, not only don't require fingerprinting, they don't even require criminal background checks for teacher license applicants. Carolyn Alexander, who works in Mississippi's teacher certification office, said her office sometimes receives anonymous calls from people who ask if Mississippi does background checks on teacher applicants. She tells them there are no background checks, and they hang up.

She feels certain these callers then apply for a teaching job in Mississippi, and that experience has made her even more certain that background checks are needed in the state.

"We're deceiving ourselves if we don't think there are perverts," she said.

In Alabama, after three years of trying, education officials were able to persuade legislators to pass stricter laws on background checks for teacher candidates. Now, applicants at all schools must undergo a national fingerprint check. Before the law passed in July, the background check was just a policy, not a law, and did not apply to private or parochial schools, according to Alabama education department spokesman Tony Harris.

Fingerprinting and background checks sometimes don't tell the whole story, however. Shayla Lever, director of child abuse prevention for the Los Angeles Unified School District, said fingerprinting might lead to a false sense of security.

"The majority [of abusers] would not have anything on file," Lever said. "Fingerprints don't indicate propensity. Pedophiles have a history of being in situations where the child doesn't expose them."

A slowly increasing number of states, like Alabama, are passing laws designed to keep bad teachers out of the classroom. In Wisconsin, for instance, legislators approved a law that's standard procedure in most states -- a law that allows school district officials to fire or refuse to hire anyone who's been convicted of a felony.

And in Minnesota, Kathy Schilla -- the parent whose daughter was molested -- was instrumental in getting a law passed in May that prohibits any person convicted of a felony sex offense from obtaining a teaching certificate.

"I had to do this for her," Schilla said in a recent phone interview. "He took away her innocence and self-esteem. What he did was horrendous." Her daughter's life has been troubled since the abuse, and Schilla won't talk about her.

While new legislation is encouraging, Douglas F. Bates, a Utah education licensing official who's considered one of the nation's leading experts in teacher misconduct issues, isn't impressed yet. "It's less than it should be in every state," he said.

Here are other ways bad teachers beat the system:

Lazy reference-checking. Arizona's regulations -- some of the most stringent in the country -- mandate that school officials contact an applicant's previous employer for references. That may sound like standard procedure for any new hire, but school districts struggling with teacher shortages sometimes do only a cursory reference check, or don't bother with it at all.

And the problem may only get worse. About 2.2 million teachers will be needed nationally over the next decade, according to federal education officials. States that are short on teachers may be lax , or late, in conducting background checks, investigators worry.

Ignoring the signs. Also in Arizona, any teacher who even suspects "immoral behavior" on the part of another educator must report it to an administrator, noted Craig Emanuel, an investigator with the Arizona Department of Education. If teachers don't report the suspicion, they can be charged with a Class I misdemeanor and could lose their own teaching certificate.

Lever said school officials need to pay closer attention to teachers to make sure problem behavior isn't going undetected or, worse yet, tolerated. In the Los Angeles district, she said, "We're very much aware of abuse perpetrated by staff," she said. "The reality is that molesters and abusers go where there are children, and the children are in the schools."

Lack of procedure. Whose job is it to handle teacher abuse allegations? Sometimes, victims don't know where to go for help.

The Los Angeles Unified School District, where the school population outnumbers the population of many cities, has its own department to handle cases in which teachers abuse students. Lever, director of the department, says she knows of no other school system in the country that has such an office.

In Pennsylvania, students or parents who are uncomfortable about making a complaint to the school principal can go directly to the state Department of Education. A complaint form can be found on the department's website -- http://www.bbpages.psu.edu/bbpages_reference/40001/400015656.html

No national data base. All state education departments are members of the NASDTEC Clearinghouse, an Internet "bulletin board" managed by the National Association of State Directors of Teacher Education and Certification. It lists educators who have had some adverse action taken against them.

But Bates, who serves as general counsel of NASDTEC, is the first to acknowledge that the list is only as good as the reporting from the states. "They're not only not reporting, they're not checking it," said Bates. "Unfortunately, there's the attitude that 'it won't happen here.' "

Also, NASDTEC's executive director, Roy Einreinhofer, believes his list includes few teachers who were disciplined before 1984, when the clearinghouse was created.

"We asked the states to go back and record as much historical data as they could," he said. "Some of them did, and some of them didn't."

The list is available only to selected state officials -- not to the general public.

Lack of cooperation among states. Only a few states -- not including Pennsylvania, Ohio or West Virginia -- have revocation "reciprocity" with neighboring states. In other words, if one state revokes a teacher's license, another state can automatically revoke the license without a hearing and also may deny an application from that teacher. Without reciprocity, state officials must conduct their own, time-consuming investigation before taking the teacher's license.

Too many deals. School officials sometimes agree to expunge records and make deals so that bad teachers will leave quietly, experts say. But in a few states, that's prohibited by law. Those laws also require that if a teacher resigns to avoid discipline, it must be reported to the state's department of education, which keeps the case on file but does not release the information. Even if the school district does keep such records, it's up to school officials whether to reveal that information.

Lack of cooperation among in-state agencies. Pennsylvania education officials asked state police to compare its criminal records to the list of certified teachers in the state. But the idea was dropped when state police said they'd charge the state education department for each name, which would have run into millions of dollars, according to Pat Fullerton, assistant chief counsel for the education department.

So state education officials rely on less efficient methods such as checking newspaper clippings to find out if a teacher has been convicted of a felony. And education department staffers attend parole board hearings and other court proceedings in case a defendant happens to be a teacher.

By contrast, Kansas law requires county district attorneys to forward every felony conviction to state education officials so they can check the names against their teacher certification list.

Lack of monitoring by the federal government. The U.S. Department of Education doesn't monitor the number of teachers accused or convicted of abusing students, or teachers who have lost their teaching certificates for any reason.

"Education is regulated by the states, not the federal government," said Dr. Nan Stein, a Wellesley College researcher.

Restrictive laws. In many states, teachers can be reprimanded only for actions that occur at school. For instance, in Fort Lauderdale, Fla., two teachers were arrested and charged in January during a raid on a sex orgy club in Pompano Beach. But they've been allowed to keep working in the school district -- although away from the classroom -- because the offense occurred off school grounds.

Kenneth Springer and Tonya Whyte were arrested in January. When school board first considered the case in early August, they voted, 8-1, to suspend them without pay. But after a public backlash over the decision, the board reconsidered and voted to keep them on salary. They're currently awaiting an administrative judge's decision on the district's accusation of immorality.

Statute of limitations. In cases of sexual abuse by teachers around the country, the state's statute of limitations often has kept charges from being filed when victims come forward years after the abuse. But some states have dropped all time limits on filing charges.

Secrecy. Students who are victims of abuse, especially boys, often don't tell anyone, research shows. Only about 7 percent of students sexually harassed by a teacher will report it to anyone, according to studies conducted by Hofstra University professor Charol Shakeshaft.

Denial. Teachers don't want to acknowledge that one of their own colleagues could be a child molester, experts say, and may vocally support a teacher accused of misconduct while publicly dismissing the alleged victim.

Parents don't want to believe that the most popular teacher in school is fondling his students. And administrators don't want parents to find out that a bad teacher is on the payroll. Educators tend to "protect the group, circle the wagons," said Dr. Dan Wishnictsky, a researcher at Winston-Salem (N.C.) University. "This is why the information is not being made public, even within education circles."

Mary Jo McGrath, a Santa Barbara, Calif., attorney who specializes in school law, noted that teachers "have a difficult time reconciling the person they know with the heinous behavior they are hearing about.

"It is often easier, and certainly more comfortable, to assume that the student is lying."